Gastro-esophageal reflux disease (GERD), which is associated with severe heartburn, affects a substantial portion of the world population. People who experience heartburn at least once a week are reportedly at an increased risk of developing esophageal cancer in their lifetime. When left untreated, chronic GERD can cause the inner lining of the esophagus to change from squamous mucosa to columnar mucosa, which sometimes includes intestinal metaplasia or Barrett's esophagus. Left untreated, Barrett's esophagus can progress to esophageal cancer, for which a common surgical treatment is esophagectomy (removal of the esophagus.)
The first step for stopping the progression of these tissue changes is to reduce the amount of stomach acid that refluxes into the esophagus. This can be done through acid suppression therapy using drugs such as a proton pump inhibitor or surgically, using a surgical procedure such as a Nissan fundoplication. The Nissan fundoplication procedure alters the anatomy of the stomach and esophagus to reduce acid reflux. Once the acid reflux has been treated, the condition of the esophagus is monitored over the patient's lifetime to watch for esophageal cancer.
It has been demonstrated that if the abnormal lining of the esophagus is removed in an anacid environment (i.e., after the patient's GERD has been treated using drugs or surgery), then normal squamous cells will regenerate and the esophageal lining will be restored. Physicians currently use a number of instruments to remove abnormal esophageal tissue, including the Gold Probe™, which is an electrosurgical ablation device available from Boston Scientific, Inc. and which is introduced through the working channel of a flexible endoscope. Another ablation instrument that a physician may use for this purpose is an argon plasma coagulator, which applies a stream of ionized argon gas to facilitate the flow of electrical current. Examples of other ablation modalities incorporated into medical instruments that may be used to ablate tissue in the esophagus include laser and other optical devices such as those used in photodynamic therapy (PDT).
A significant problem with prior art ablation devices used to ablate abnormal regions in the mucosa of the esophagus is the surgeon's lack of adequate control over the size, shape and depth of the treated region. Prior art devices that use electrodes to ablate abnormal regions in the mucosa of the esophagus also provide limited visibility of the treated tissue, thus potentially resulting in damaging adjacent healthy tissue, including healthy tissue under the mucosal layer. Further, problems with prior electrosurgical devices used to ablate tissue in the esophagus arise because such instruments ablate tissue directly beneath the device electrodes. In particular, because the electrodes are opaque, the physician cannot monitor the degree to which tissue under the electrodes is ablated, making it difficult to determine when to stop applying electrical current. Further, since ablated or charred tissue tends to stick to electrodes if treated for too long, removing the instrument may avulse some of the treated tissue away from the wall of the esophagus and cause undesirable bleeding.
The esophagus is a flaccid, tubular organ that has many folds and irregularities on the interior, mucosal lining, especially if diseased. Another significant problem when electrosurgically treating diseased tissue of the esophagus is supporting the walls of the esophagus in order to bring the diseased tissue into intimate contact with the electrodes of the electrosurgical instrument. In addition, the esophagus is not a static structure, but rather contracts frequently due to muscular, peristaltic action. Another consideration when treating the interior lining of the esophagus is post-procedural pain due to tissue trauma associated with passage of instrumentation through the constricted, curved passages of the throat, especially during intubation of the flexible endoscope.
Therefore, an improved medical instrument for treating diseased tissue in the mucosa of the esophagus would provide a physician with the ability to accomplish one or more of the following:                To position accurately the surgical instrument over the tissue region to be treated, and to do so as atraumatically to the patient as possible.        To ablate only the tissue in a specific, predefined area, which is visible to the surgeon before and during the ablation (and not treat tissue that is under the treatment electrodes).        To stop ablation at the appropriate time in order to control ablation depth.        To support the walls of the body lumen and bring tissue to be treated into intimate contact with treatment electrodes.        